One of the most challenging questions that have been left unanswered to this date is that regarding human evolution and geography. From the sociological point of view, it has long been known that specific populations can be differentiated from each other based on their religious backgrounds. On the other hand, forensic science employs language in grouping human population. In the field of human genetics, there is currently credible information that facilitates the understanding of how the entire human population evolved through time.
The recent completion of the Human Genome Project resulted in the generation of the actual deoxyribonucleic acid (DNA) sequence of a human cell, with the hope that every disease could be associated to a particular gene in the sequence. Alongside this discovery, other genetic features have been uncovered in the DNA sequence, including small nucleotide polymorphisms which serve as signatures to specific biological phenomenon. In Olson’s chapter entitled “God’s people: A genetic history of the Jews,” the evolution of this population was described in terms of selection, environmental factors, adaptation and migration (Olson 107).
The chapter supported this description with reports generated from haplotype reconstruction and tracing of Aaron’s Y chromosome. Through DNA sequencing analyses, it is now possible to reconstruct the origins and migrations of specific populations based on the presence or absence of genetic markers in the human genome sequence. The most interesting part of the chapter is that genetic changes in the Samaritan population can be correlated to their historical account, including the time when these individuals were under persecution by the Roman government. This historical event resulted in a significant decrease in their population size.
In response to the change in population size, the Samaritans underwent what is genetically termed inbreeding, which is simply the action of consanguinity. Despite common notions that consanguinity results in serious health risks, this population survived through thousands of years. One major observation among the Samaritans is that these individuals physically appear similar and this is mainly due to inbreeding. Interestingly, the expected medical diseases that are commonly brought about by intermarriages did not develop in the next generations and this may be due to the selection against these defective genotypes.
Another process that could be associated with this scenario is the bottleneck effect, which selectively retains the beneficial genes to the next generation. Today, it has been estimated that approximately 13 million Jews are living in the Middle East. The contemporary Jews are technically grouped into Ashkenazi or non-Ashkenazi, based on their ancestry through regions around Europe. These individuals are a good population to follow in terms of genetic history, since this population carries a natural history of migration and evolution through time.
The non-Ashkenazi Jews are considered as the highly migratory subpopulation, resulting in a diverse culture. On the other hand, the Ashkenazi Jews generally remained in the same region, thus preserving their genetic makeup. This geographical history thus resulted in the identification of specific genetic mutations and diseases that are inherently observed among members of this population. The chapter also attempted to describe the effect of founding mutations, which are initial mutations that have occurred early in time during the migratory and settling era of the population.
The subsequent generations of this population resulted in the presence of the same diseases and mutations, the most possible explanation for this is that these formerly de novo mutations have been fixed in the genome sequence of the offspring. It should be understood that genetic mutations occur in germ cells, as well as in somatic cells, and these have the propensity to be passed on to the next generation through the genetic laws of independent assortment and segregation.
The analysis of sequences derived from mitochondrial DNA have also revealed that the founder mutations reported among the Jews were transmitted through a matrilineal route (Behar 2062). Using mitochondrial DNA tracking, genetic analysis can generate estimations of the time of fixation of a specific genetic mutation in this population. The continuous geographical changes of the members of this population further exert its impact on the genetic fixation and phenotypic frequencies of these mutations, resulting in the current genetic conditions of this group.
The genetic pool of the Jews thus reflects a microenvironment wherein genetic changes, alongside environmental effects and migration could be correlated with each other. There is still great debate with regards to the genetic history of the Jews. As Olson has indeed mentioned in his writing, all human beings are similar in the genetics aspect and being a Jew is simply based on how an individual feels about himself. This maybe true, yet in time there will still be more information that will be gathered from genetic assays on different populations around the world.
The current information that has been established is that there are three founding mutations that have been identified in the Jews and each mutation reflects the origin or migratory pattern of each subgroup. However, the exact direction or genetic drift of each migratory pattern still needs to be further investigated. There is a need for a comprehensive genotyping of more individuals of each human population in order to fully understand the historical, as well as geographical account of human evolution and speciation. Each existing population must have been derived from an original group of individuals that existed in time.
2. The article entitled, “Jewish legacy inscribed on genes” authored by Karen Kaplan describes the account of Gregory Cochran regarding the genes of Jewish individuals (Kaplan 3). One of his claims is that Ashkenazi Jews are more prone to serious medical disorders due to the common mutations that afflict this specific population. One of the highly publicized medical disorders that commonly occur among Ashkenazi Jews is Tay-Sachs disease, a neurological childhood condition that leaves an individual disabled and complications result in difficulty of these individual’s to lead normal lives.
Another common genetic disorder affecting Jews is Canavan disease, which involves the deterioration of the brain tissues, resulting in both morbidity and mortality in young Ashkenazi Jewish children. Niemann-Pick disease is another serious medical condition that is often reported among this specific human population and this disease is associated with the significant accumulation of fats in the particular organs such as the brain. Unfortunately, these aforementioned medical disorders result in mortality of an Ashkenazi Jew at a very young age.
Another medical disorder that occurs frequently among Ashkenazi Jews is torsion dystonia, which is a movement disorder that involves changes in the tissue consistency of the brain. The accumulation of plaques in the brain results in the involuntary jerking and twisting of parts or even the entire body of the afflicted individual. Cochran claims that these common medical disorders affect Ashkenazi Jews in particular through a specific genetic makeup that still has yet to be uncovered.
It is also of interest to know that these common disorders are of neurological origin, which means that the central nervous system of an individual is affected. Thus, these disorders can either affect the brain, the spinal cord, or any of the smaller neural cells that are connected or associated with the nervous system. In order for the public to better understand his claim, Cochran even compared this association to that of sickle cell anemia, which is a severe blood disorder that is commonly observed among African Americans.
This genetic blood disorder results in the difficulty to transport oxygen to the rest of the parts of the body, as the red blood cells are distorted in shape, from the normal ovoid shape to that similar to a sickle. Comprehensive scientific research has established that a specific mutation is responsible for the generation of a sickle cell-shaped red blood cell, which in turn is commonly present in individuals of African American descent. Another claim of Gregory Cochran is that despite such serious medical disorders that commonly affect Ashkenazi Jews, a positive observation is also significantly present in this human population.
Cochran claimed that Ashkenazi Jews are highly intelligent, as shown by intelligence quotient (IQ) scores of children of this ethnicity. He thus proposed that the predisposition of Ashkenazi Jews to mutations in gene associated with brain conditions also results in a high level of intelligence. Kaplan’s article further supports Cochran’s claim of intelligence and gene mutations with the historical accounts of how Jews lives through the centuries. The activities mainly involved migration, trading and other forms of business, all of which were highly successful.
Kaplan supported Cochran’s claim by saying that these business transactions can only survive if the individuals involved were highly intelligent and since most of the activities were led by Ashkenazi Jews, then it is also likely that the intelligence “phenomenon” may have existed early on. Unfortunately, the claims of Cochran still need to be tested on a large population of Ashkenazi Jews before this can be proven and accepted. As Kaplan accounts in her Los Angeles Times article, the report of Cochran was an outright reject in the first journal that he and his collaborator, Harpending, submitted to.
However, another journal that supports theories without substantial experimental evidence, Journal of Biosocial Science, published their claim. The claim of high intelligence among Ashkenazi Jews needs to undergo comprehensive investigation first before it can be fully accepted in the field of science. Similar to the genetic establishment of the neurological diseases that commonly affect Ashkenazi Jews, this claim was further strengthened after several years of scientific research in genetic laboratories.
Patients positively diagnosed with the neurological disease were checked with regards to other clinical features. In addition, their DNA was extracted and the specific genes responsible for generating the disease were sequenced. In case a DNA mutation was identified in the genes, these were compared to other patients’ DNA sequences. Any other common features among thousands of patients were correlated and compared, thus resulting in what has now been established as a predisposition of the disease in this human population.
It is thus important that the same meticulous type of investigation be conducted with regards to intelligence. However, the search for the answer to this claim may be more difficult because intelligence has been established to be influence by several factors. Scientists and psychologists have earlier established that the multi-factorial origin of intelligence makes any effort in tracing the source of intelligence to be ultimately difficult.
Intelligence can not simply be generated through the genes because environmental factors can also affect an individual’s condition, including his mental state. There are a number of twin studies that have been conducted for several decades that employ the procedure of separating each of the twins are bringing each individual up in a different environment. Since the genetic makeup of twins is entirely the same, then any claims on intelligence genes can be validated in such experimental conditions.
Unfortunately, twin studies have proven that a child who was brought up in an environment filled with violence and anger tend to be poorly developed in intelligence. On the other hand, the twin sibling who was raised in an environment that was filled with love and support grew up into a very intelligent and mature individual. It is thus difficult to prove Cochran’s claim that Ashkenazi Jews are far more intelligent than other human populations, because there are so many factors to consider before one can claim that a specific entity influences that state of thinking.
Another issue that would emanate from such claim is that other cultures and ethnicities would perceive such proposal as a form of discrimination or indifference to other human populations. Claiming or even proving that a certain human population is highly intelligent does not help in the global cooperation between countries. In addition, the establishment of this claim will not save lives, just like the other efforts that employ genetic technologies in screening for specific mutations that would tie a particular phenotype to a particular genetic sequence.
Proving the high levels of intelligence among Ashkenazi Jews will only spark anger and outrage from other cultures. It is thus good that Cochran feels that there is no need to prove his claim through the use of experimental evidence. It would also be safe and for the best of the rest of the world to leave Cochran along with his claim and let other people speculate on his unsupported claim. The application of genetic analysis on human population has been regarded as a novel and revolutionary addition to the methods in studying human evolution and speciation.
The information that can be generated by this technology can be very sensitive and effective, yet there is still a need to employ human intervention and compassion with regards to which specific questions need to be addressed. Genetic analysis in connection to medical disorders can be very helpful in diagnostics and treatment, as well as for saving lives, but genetic screening other social factors such as intelligence will only spark bias among individuals around the world.
Works Cited Behar, D. M., Metspalu, E. , Kivisild, T. , Rosset, S. , Tzur, S. , Hadid, Y. , Yudkovsky, G. , Rosengarten, D. , Pereira, L. , Amorim, A. , Kutuev, I. , Gurwitz, D. , Bonne-Tamir, B. , Villems, R. and Skorecki, K. “Counting the Founders: The Matrilineal Genetic Ancestry of the Jewish Diaspora. ” PLoS ONE 3 (2008): 2062-2087. Kaplan, K. “Jewish Legacy Inscribed on Genes? ” Los Angeles Times 18 April 2009. Olson, S. Mapping Human History: Genes, Race, and Our Common Origins. San Francisco: Harcourt Publishers, 2003.
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